blue-sky

American  

[bloo-skahy] / ˈbluˈskaɪ /

adjective

1. fanciful; impractical.

   blue-sky ideas.

2. (especially of securities) having dubious value; not financially sound.

   a blue-sky stock.

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blue-sky British  

noun

1. (modifier) of or denoting theoretical research without regard to any future application of its result

   a blue-sky project

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verb

1. to theorize (about something that may not lead to any practical application)

Etymology

Origin of blue-sky

First recorded in 1890–95

Example Sentences

For hours on a crisp, blue-sky day, kite flyers mingled with sign-wavers, sharing space on the National Mall as they pursued their dueling missions.

From Barron's • Mar. 28, 2026

His research is the bluest of blue-sky: he uses quantum computers to predict how sub-atomic particles behave.

From BBC • Mar. 17, 2026

“This should put a capper, in our opinion, on blue-sky hopes for substantial multiple expansion,” he wrote.

From MarketWatch • Feb. 5, 2026

Strauss, a financier in the 1920s of the city’s skyline, summed up the blue-sky optimism: “New York cannot be held back in her growth and development as the supreme city in the world.”

From The Wall Street Journal • Nov. 8, 2025

The pond on my right was frozen over, and an unbroken plane of white stretched to the blue-sky horizon.

From "Anthem of a Reluctant Prophet" by Joanne Proulx

Related Words

• absurd
• bizarre
• extravagant
• fantastic
• fantastical
• fictional
• imaginative
• offbeat
• preposterous
• unreal
• whimsical